Radio direction finder



Jam.- 4, 1938. c. s. FRANKLIN 2,104,075

RADIO DIRECTION FINDER Filed Jan. 16, 1935 y 2SheetS-AShee'b lv i {f2/31415121716@ 3956005 DISCHARGE f y' INVENTOR.

CHARLES S. FRANKLIN BY vf/@W ATTORNEY.

Jan. 4, 1938. C, s FRANKUN 2,104, 075

RADIO DIRECTION FINDER Filed Jam1 1e, 1935 2 sheets-sheet 2 CENTER 0F F0 TA 7/0N v Ffm/)m5 INVENTOR.

.I CHARLES S. FRANKLIN BYs l ATTORNEY.

Patented Jan. 4, 1938 UNITED STATES PATENT OFFICE RADIO DIRECTION FINDER .Application January 16, 1935, Serial No. 22,044 In. Great. yBritain .January 27, 1934 7j "Claims.

. This invention relates" to ydirectional y'radiofreceiving Ainstallations'xsuitablei for use for-'positionifirding .J and. navigation purposes y generally. L'The objectrofltheinventionis tozr'provide a irelativelysimplc andsatisfactory receiving inr stallati'on iwhichfcan receive signals from .almost any number ."of- Ldiiierently 'positioned transmit- #ters A simultaneously vfand indicate the directions fo'f these Y transmitters ""'with 'i respect l to z the "re- :.ceiving installation. j --According to..`this:.:invention` a zwireless receivlingL installation comprises a .plurality of direc- 2tional receiving'eaerials vor aerial systemsv having maximumf `directivityiin1 different directions with respectito a :central point; means for translating signals received uponrsaid :aerials'or systemsv into .visible.indications,-andmeans for arranging'fsaid zvisible indications-y infsuch Amanner .that` each inl dication correspondszin positionto the .direction yLof directivity'" of the receiving aerialzfor system Y sfromfwhichthat indication isderived. 11n this way the result'fachieved is that :each :indication yproduces, asfit yWerepa point vupon Lan imaginary "curve'connecting theindications so thattheI di- "rectionfof thetransmitters which hasfgiven rise to the received signals, will be. indicatedby the v shape. of said imaginarycurve.

.I'n.carrying out. this invention, itis preferable rtoemployI a 'directionalfaerial such-.as shown and described in.my'U..S. Patent 27,053,658, issued fSeptember 6,1936. In carrying out thepresent fiinvention, however, the `use `of such serials is .not

absolutely essential. Y

'Where afreceiving installation vaccording to j .this invention isiemployed for direction indicating and. position finding for-land; and sea work, fthe directional.receivingwaerials or systems will 'generally be-arrangedin a circle about a central point. Where, however, aerial-navigation is in question; i. fe., fwhere directional indication in :three -dimensions is required; ,the -aerials -orsys- I l tems--wouldy ordinarily .be placedcn .the. surface of=-an. imaginary sphere.

The inventioniswillustrated in andfurther ex- 1lplained. .in-` connection vwith the vaccompanying f schematic. a-nd. .diagrammatic .drawings,..in which .Fig. `1 shows .diagrammatically -a system of ,.aerialseach connected with. a receiving` system; 2.shows Ldiagrammatically a .curve of. field `strength .values `for a directional beam;

`Fig. 3 showsa modified arrangement of aerials of the same' type otherwise shown in Fig. 1, and, Y -Fig.'4 shows Va modification ofthe invention 'in vwhich a' com'mutatorfswitchl `-isv employed.

" Referring to'Figure 1, v`vvhi'chfshows one .way

(Cl. Z50-111) vof carryingv out this invention, a plurality 'oi' aerialfsystems in accordance With the aforementioned U.1S.' Patent 2,053,658, are arrangedeach to point in a .different direction. In -the ex- -ample illustrated, there are 18 aerials-indicated by heavy lines labeled A1 to A18, arranged in` a segment offa' circlev (whose centre is indicated by Ythe reference C) each pointing in a different radial direction. Each aerial isabout fourtimes the working Wave length'long and .theisaidl aerials arespaced apart :by approximately' 0.8 of the Working Wave length.Y The angle between successive `aerials is '7.5 and that between suc- V*cessive pairs of'aerials is 15. The polar curveof a pair oflthe'aerials (the aerialsfAg and Amare# taken for purposes'of exemplication) 'is shown in conventional'form inFigure' 2, the curve beving a curve of iield strength values. Each kpair of aerials is `connected through `a feeder "F1-F9v commonv to that pair. In contrastfwith the heavy lines which represent the aerials these feeders arerepresented by light linesand'they are eachv connectedto a separate receiver Ri--Ra actuating some form. of visual indicator `I1--I9, eng., a meter indicating the strength of Vthereceived'signals. .The indicators are mountediside 'by side with their "indicating members so positioned'as to move at right angles to a horizontal scale S which is marked out in directions correspondingv to the 'directions in which thek various aerials' point. Suppose with such. an instal- 'lation that incoming signals arrive from the two directions X and'Y, then the indications of the indicators will be more or less as shown in Figure l by the illled in portions oi the vertically disposed tubular elements 11-19 which are'preferably gaseous discharge'tubes. Thusy-when signais are received from two different stations in the directions X and Y, the imaginary curve (shown in' ne lines in Figure 1) joining the indications given will have peaks corresponding to the 'directions of the two received stations. There are various forms oi` indicators whichmay be used in carrying. out the invention; for example, the indicatorenergized in dependence.. upon theoutput'irom each aerial may be in the `form of a vacuum tube tted with electrodes and larranged to give a column of light of length substantially proportional to the energy output from the .appropriate aerial. Such indicators are schematically represented in Figure l.

With aerials as employed in Figure 1,' the directions of incoming signals cangenerally'fbe estimatedito aboutS to 4 degrees, `if necessary. Where l the signals come fromV a :plurality .of

transmitters sending continuous dashes, the registrations on the indicators tend to overlap unless the angle between adjacent directions is more than about 45 degrees. If, however, each transmitter is sending a distinctive call, so that reception from all is not always simultaneous, then the direction of each and theangle between them can be judged to about 3 to 4 degrees.

It will be observed that the discriminating power depends on the sharpness of the polar.

curves obtained with the elementary aerials or systems employed. It follows that the shorter the wave length, the smaller will be the space occupied by the aerials or systems or alternatively the greater will be the discriminating power obtained for equal space occupied. A discriminating power, as obtained with the arrangement of Figure 1, would be suiicient to -allow a ship, for instance, to be guided between two beacons. The aerials or systems may be erected to cover any desired arc in the horizontal or vertical plane, and may be arranged to be rotatable as a whole so as to enable observations to be taken in any particular arc of a circle. A reduction in the number of aerials or systems and of the space occupied may thus be elected at the sacrifice of what may be called the iield or arc of observation for 4any one position of the aerial installation as a whole.

In cases where direction in one plane only is required (say the horizontal plane) space can be saved by arranging the aerials singly or in groups above one another. For example, the eighteen aerials shown in Figure 1 may be rear ranged as indicated in Figure 3. Here the aerials A1 to A6 are arranged under the aerials Av to A12, while above these are arranged the aerials A13 to A18. The directions of pointing of the aerials in Figure 3 is the same as in Figure 1, but

the area occupied by them is much reduced at the expense of greater height. In Figure 3 the indicators and scale are not shown.

Where directional indication in three dimensions is required, the indicator system is preferably such that indication is given by a spot of light whose character, e. g., color and/or intensity, is arranged to be changed in dependence upon the strength of the signal received upon the aerial or system actuating the indicator.

A convenient form of indicator which may be employed is a cathode ray tube of the kind in which the ray is projected upon a iiuorescent screen to give a visible indication.

In another way of carrying out this invention, as shown in Fig. 4,.-a single receiver is employed and the aerials or aerial systems are arranged to be actuated successively thereby through a suitable form of continuously running commutator switch or coupling device. The commutator is shown having a brush 3 which sweeps over different segments 4 each segment being connected tol one of the conductors Fi-Fs respectively. The brush also sweeps over a collector ring 5 thereby to connect different ones of the segments 4 with the receiver 6. The brush 3 'and the luminous discharge tube 1 are rotated in unison so that as the tube 'I is lighted up by signals different directional indications may be made depending upon the direction from which the signals are received on the different antennae feeding to the diiierent conductors Fi-Fs. The output of the receiver is utilized to give indications at diierent parts oi' a directional scale, the arrangement being synchronous so that when the receiver is connected to an aerial or system pointing in any particular direction the indication appears opposite that part of the scale corresponding to the same direction. If the succession of aerial connections is sufficiently rapid the output curve of the system will appear continuously on the scale and will show directly the direction or directions of a station Y or stations being received.

It will be at once apparent that if two or ,more stations are being received simultaneously,

the direction of both will be indicated simultaneously providing-as will normally be the casethe angles between them are sufficiently large.

The indicating mechanism employed may be of any suitable kindbut should preferably be such as to enable the desired information as to direction to be immediately seen by direct inspection of the indicators, i. e., without having to record (graphically or otherwise) their indications.

The invention may be utilized for general nagivation purposes and one application which may be mentioned is to aircraft. For this application the invention may be utilized to provide direct indication on an aircraft of the relative angular positions of a number of transmitters near which the aircraft is passing. In such an application the aircraft would be iitted with indicating apparatus as above described and arranged to be energized by a plurality of directional aerials arranged over a portion o-f 1 an imaginary spherical surface. For such application of the invention the wave lengths employed should be as small as practicable in order to reduce the sizes of the aerials to aminimum consistent with obtaining the required discrimination between transmitters.

For land and sea workwhere it will generally be sufficient to arrange the aerials in a circle-longer wave lengths can be used.

Having now described and ascertained the nature of my invention and in what manner the same is to be performed, I claim:

1. A receiving system comprising a plurality of directional receiving aerials arranged in pairs, each pair havingV its axis of maximum directivity response oriented at an angle to such axes of the other pairs, means including luminous discharge tubes arranged in order for indicating diiferent directions from which signals may be received on said aerials, said tubes having the characteristic that a column of light of variable length may be produced therein, operating circuits connecting each pair of said aerials with an appropriate one of said luminous discharge tubes, and a power supply connected to said operating circuits, said circuits being arranged to feed potentials to said discharge tubes proportionately to the amplitudes of the signaling energy collected by said aerials.

2. A system in accordance with claim 1 and having a graduated scale along which said luminous discharge tubes are positioned, whereby the indications made by said tubesV may be translated into compass-chart directions.

3. In a device of the class described, a plurality of directional receiving aerials each differently oriented so as to collect a maximum of signalling energy from a direction along its own axis and having the respective axes thereof disposed at substantially equal angles, one to the next, about a common center, and a signal responsive device individually connected to each aerial, the plurality of said devices being arranged adjacent one another in the same order as their corresponding aerials, each responsive device comprising a luminous discharge Vtube having the characteristic that when suitably excited it produces a column of light of variable length, and means operating in dependence upon the amplitude of the energy collected by a given aerial for determining the length of said column of light which is caused to emanate from said discharge tube.

4. A device in accordance with claim 3 and embodying further means for receiving directional signals on a selected one of said responsive devices at a sufcently high speed to maintain persistence of vision of the indication 15 therein.

5. A device in accordance with claim 3 and further characterized in that the aerials are arranged in different groups each group being at a diierent level with respect to the aerials in other groups.

6. A device in accordance with claim 3 and Vfurther characterized in that said aerials are maintained at predetermined angles one to another and means are provided for orienting theV entireV system of aerials about a center of rotation.

'7. A device in accordance with claim 3 and having means for maintaining said aerials in such positions as to be directionally oriented one with respect to another in three dimensions.

CHARLES SAMUEL FRANKLIN. 

